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the polarimeter and the saccharimeter
The polarimeter constituted one of the instrumental answers
for the study of the properties of light, specifically the
understanding of the physical optics phenomenon of light polarization.
That is, the effect created by light waves of a ray vibrating
on a single plane when the ray hits on certain materials.
The research carried out in the beginning of the 19th
Century extended the analysis of the effects produced by polarized
light from crystalline solids and other optically active substances
of animal and plant origin, which showed the capability to
modify the plane of light polarization. Immediately, these
ideas were translated into the creation of new instruments,
such as the polarimeter. Geologist William Nicol greatly contributed
by devising a prism made of two pieces of Iceland spar crystal
that allowed light polarization. The application of Nicol’s
prism to both ends of the polarimeter allowed the analysis
of the optically active substance placed in the middle when
a turn was operated on the light polarization plane. The value
of this turn could be measured in degrees, thus facilitating
the calculation of the concentration of the given substance.
The objects we show, two polarimeter-saccharimeters and a
Robert Bunsen burner which provides the ray of light, allowed
the transference of techniques and the adaptation of new applications
to distinct disciplines, such as medicine, pharmacy and other
related industries.
One of the substances that concentrated great attention on
the second half of the 19th Century, due to medical and industrial
reasons, was sugar. The saccharimeter was developed upon the
base of the polarimeter as an instrument for the measurement
of the quantity of sugar in a given substance. At the end
of that century, physicians and pharmacists to determine the
presence of glucose in urine and facilitate the diagnosis
of diabetes, among other aspects, used those devices. A solution
made by the combination of a reagent in urine was subjected
to the ray of light and, on the basis of the observed rotation
on the polarization plane, it was possible to determine the
concentration of sugar in a substance such as urine.
This technique was nevertheless quickly relegated from the
medical and pharmaceutical field to other customs and industrial
fields, due to distinct factors such as: the complexity and
confusion of calculations –manufacturers adopted different
saccharimetric scales- and the development, at the beginning
of the 20th Century and of great use till the 1940s, of simple
fermentation saccharimeters –by M. Einhorn and Th. Lohnstein-,
which allowed to know the values of glucose without the need
of calculations, as well as biochemical microprocedures, such
as the one tried by I.C. Bang, which opened up the range of
substances to study in the field of physiological chemistry.
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© Official Medical Association of Barcelona 
